Reluctance chain sensor and method of measuring the chain elongation

Abstract

A chain sensor comprising at least one coil and a device for measuring the chain elongation comprising two chain sensors and a control unit, are provided. In addition, a method of measuring the chain elongation of a chain with two chain sensors arranged along the chain in spaced relationship with one another is provided. The chain sensor comprises at least one first reluctance sensor. The first reluctance sensor has a magnetically conductive yoke body comprising a central leg and two yoke legs extending laterally thereto. The yoke legs are each provided with at least two teeth, the teeth of the yoke legs being adapted to be arranged in closely spaced relationship with a chain. The first reluctance sensor includes at least one permanent magnet.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application claims priority to foreign European patent application No. EP 14000520.8, filed on Feb. 13, 2014, and to foreign European patent application No. EP 15000167.5, filed on Jan. 21, 2015, the disclosures of which are incorporated by reference in their entireties.FIELD OF THE INVENTION[0002]The present invention relates to a chain sensor comprising at least one coil as well as to a device for measuring the chain elongation comprising two chain sensors and a control unit. In addition, the invention relates to a method of measuring the chain elongation of a chain with two chain sensors arranged along the chain in spaced relationship with one another.BACKGROUND[0003]Chain drives, in particular those based on roller chains, are used for the purpose of driving and conveying in industrial applications, wherein a plurality of chain strands being used in various fields of application. A chain drive unit normally comprises an endlessly ...

AI Technical Summary

Benefits of technology

[0010]Therefore, it is the object of the present invention to eliminate or reduce the drawbacks of the prior art devices and methods for monitoring a chain elongation caused by wear, and to provide to this end a suitable sensor and a measurement device as well as an improved method of measuring the chain elongation of a drive chain.

[0011]In the case of a chain sensor according to the present invention, at least one first reluctance sensor is provided, said reluctance sensor having a magnetically conductive yoke body comprising a central leg and two yoke legs extending laterally thereto, the at least one inductive coil being preferably arranged on the central leg, the yoke legs are each provided with at least two teeth, said teeth of the yoke legs being adapted to be arranged in closely spaced relationship with said chain, and said reluctance sensor further including at least one permanent magnet, preferably at least two permanent magnets, which are each arranged on a respective yoke leg and / or on different sides of said at least one coil. In addition, when at least two permanent magnets are used, it may make sense to position said permanent magnets symmetrically with respect to the central leg. The arrangement of the reluctance sensor in comparatively closely spaced relationship with one side of a chain—the yoke body may here be arranged parallel to the chain link plates of the chain and the projections or teeth of the laterally extending yoke legs extend preferably up to a point between the chain link plates—allows the formation of closed magnetic circuits via the reluctance sensor and the chain with a comparatively low reluctance, i.e. a low magnetic resistance.

[0012]For improving the magnetic conductivity of the reluctance sensor, the almost crescent-shaped yoke bodies may be configured such that they are easily permeable to the magnetic field of the developing magnetic circuits. They may e.g. consist of a magnetically soft iron core having a low magnetic resistance or minimum reluctance. The magnetic circuits induced via the at least one permanent magnet along the lateral yoke legs generate a voltage at the coil, e.g. on the central leg of the yoke body, only one of the closed magnetic circuits being conducted substantially via the coil, whereas the other closed magnetic circuit is short-circuited beyond the coil via the teeth of the associated yoke leg and the chain.

Problems solved by technology

Drive chains are, in operation, subject to wear through the relative movement of the individual components in the chain hinge and to other various chain elongation factors, such as initial elongation, stretching, bearing slackness and bearing abrasion.

These wear and elongation factors result in an elongation of the chain and, in the end, lead to a failure of the drive unit.

Hence, chain wear and, consequently, the failure of the drive unit cannot be predicted with certainty.

The high investment cost of such fully automated machines and systems necessitates the constant use of the latter with the least possible number of inadvertent downtimes. Such inadvertent downtimes lead not only to direct financial losses but also to indirect problems, such as the interruption of the logistics chain and even an incapability of observing delivery times, and thus to further financial losses.

However, the use of wear-prone chain drives cannot be dispensed with in the foreseeable future, since there is no alternative that could be used for driving such industrial systems and for conveying products.

In addition, even minor wear of the drive chains in automated machines and industrial plants necessitates a manual readjustment of sequences of operations that are synchronized with the chain position.

However, a precondition for this is that, on the one hand, a chain tensioner is actually required or rotary position sensors can actually be used and, on the other hand, that these elements are then influenced by wear and chain elongation, respectively.

Hence, such methods must be calculated and adjusted with respect to the respective case of use and with respect to the effect of the measurement results and, consequently, these methods cannot be applied generically.

In addition, both said methods measure not only the direct wear-dependent chain elongation but also the wear of the chain wheels.

In addition, optical sensors are, in many cases of application, not suitable for practical use in driving and conveying systems, since the industrial surrounding conditions contribute, due to dust and dirt, to a possible failure or incorrect measurements of the optical sensors.

Inductive sensors exhibit, in addition to a switching sensitivity in the direction of measurement, also an inherent switching sensitivity perpendicular thereto, so that inductive sensors are not only sensitive to vibration but they also tend to execute incorrect measurements.

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